Flexibility in a house is usually more of a concept than a physical reality. But in this house by dRMM in the Suffolk countryside, flexibility, or changeability, is a literal condition of the building design. Its remarkable achievement is not in any new form, since planning guidelines dictated strict limits as to height (7.2 metres) width (5.8 metres) and style (the local agricultural vernacular). Here the great flexibility comes from materials and function, a series of buildings that are traditional in aspect, but that are transformed by the changing position of a giant moveable outer structure. The main areas of the house - guest annex, garage, services, living space - are accommodated in a linear arrangement of rectilinear, pitched-roof buildings, shapes that can be traced to early medieval and Romanesque structures. So the basic premise of the house is very rooted to historic antecedents. Even the fully glazed living space at one end of the site retains a traditional farmhouse profile. But here the regularity ends, as materials were varied over the three structures - timber in natural hue and stained black, red rubber membrane and glass. Then the 20-ton sliding shell moves over these structures, changing both the appearance of the small complex of buildings from the outside, and the views, light and feel of the internal spaces. Between the guest annex and the main house, the garage sits off axis, leaving a gap between buildings for a courtyard. As the shell moves, the glazed living space becomes transformed, completely or in stages, the courtyard is covered or revealed, and an upstairs bathroom/terrace can be enclosed or left to the open air. How and when the shell is used is entirely up to the residents and can be varied at any time of day depending on the amount of sun/heat desired with just a click of a standard remote-control device. On warm days, the shell can cover the glazed living space completely, leaving the terrace and courtyard exposed to the sun. In the evening it can be moved back to enclose those open spaces and relieve some of the thermal gain from the glass house. In winter the glass can receive full winter sunlight during the day and retain any thermal gain when covered at night. And since the windows and skylights in both the stationary structures and the shell are set on a 1-metre grid system, those openings can be aligned at intervals as the shell is moved, offering many opportunities to vary the perspective from the house onto the landscape. The inspiration for the giant sliding element arose from architect Alex de Rijke’s wish to “put mobility into the design, so that the mobile part would change the character of the fixed parts”. So it wasn’t what the house looked like that would be radical, but how it could change perspective, transparency, seclusion. In keeping with the agricultural heritage of the site, de Rijke says the moving shell was informed by the giant doors on barns, heavy farming machinery and old Dutch barn buildings that have adjustable roof elements that can be raised and lowered according to the volume of the harvest being stored. The sliding shell is a smart monocoque construction. A steel frame with timber infill, it is clad in a larch rain screen with waterproof sheet paneling on the inside, and it houses all the electric motors on bogeys in the wall thickness. The 16-metre long, 7-metre high structure moves from one end of the 28-metre length of buildings to the other in 6 minutes; its motors charged when the shell is “parked” by regular 12V batteries. Other aspects of construction were also kept relatively simple. The bedroom/service block of the house was created from modular cassette construction, as were the annex and garage, while the glass house utilizes a generic curtain-wall glazing system. All the elements, apart from ground works, internal fixtures and external cladding, were prefabricated and assembled on site. And while a 20-ton moving shell might seem like an architectural extravagance, the house is conscious of thermal efficiency, with the moving roof allowing passive solar energy to be captured and stored. It also uses ground-source energy, photovoltaic panels, and (eventually) a wind turbine to power the moving structure. Here the genius has not been to raise a loud burst of virtuosity on the skyline but to accomplish an extraordinary feat (changeable architecture) in the guise of the tranquil and the ordinary.